1. Field of the Invention
The present invention relates to a motion damper. More specifically, the invention relates to a motion damper used in connection with vehicle safety systems.
2. Description of Related Art
Conventional dampers are used to limit the transfer of kinetic energy between two connected objects. In today's world, dampers are used in a wide variety of applications. For example, shock absorbers in vehicular suspension systems use a common type of damper. These suspension systems use a spring, such as a steel coil, to allow each wheel to move up when the wheel encounters a bump, and to rapidly move back down after the wheel passes the bump. However, if only the spring were used in the suspension system, the vehicle would bounce up and down several times after each bump is encountered, making it uncomfortable to ride in the vehicle and also making it difficult to control the vehicle. The danger of this situation is amplified significantly if a surface on which the vehicle is operated is coated with rain or snow. Thus, the suspension system needs a way to dissipate the energy stored in the spring after the wheel encounters an aberration. A damper performs this function and limits the transfer of the kinetic energy, or vibrations, of the wheels of the vehicle to the passenger compartment of the vehicle.
Conventional dampers have been designed in many different ways. One type of damper involves a piston tightly fitted within a chamber. The piston has a head and an arm connected to the head. The piston head slides within the chamber. Seals around the perimeter of the piston head prevent leakage of the fluid between the piston head and the chamber wall. Thus, the piston head divides the chamber into a first and a second sub-chamber. The piston arm protrudes out of an opening in the chamber. Again, seals are required to prevent fluid leakage through the opening. The piston arm is connected to a first object, such as the wheel of a vehicle, while the chamber is connected to a second object, such as the frame of the vehicle.
A volume of fluid, often oil, is disposed within the chamber. A bi-directional limiting port in the piston head permits the controlled transfer of fluid from the first to the second sub-chamber and vice versa. The limiting port may be designed to allow fluid to flow through the piston head at varying rates. A small limiting port provides for relatively slow transfer of fluid between the sub-chambers and inhibits virtually all oscillation, thus providing a firm ride and nimble handling when used in a shock absorber for a vehicle. A large limiting port, on the other hand, permits rapid transfer of fluid between the sub-chambers and, thus, yields a smooth ride when used in a shock absorber.
In an alternative design, two unidirectional limiting ports are positioned in the piston head. One port permits the fluid to move from the first sub-chamber to the second sub-chamber, while the other port permits the fluid to move from the second sub-chamber to the first sub-chamber. Using two unidirectional ports, a disparate damping effect may be provided, depending on the direction the piston head moves within the chamber.
It takes energy to force the fluid through the limiting port or ports. This energy is converted into thermal energy, i.e., the fluid is heated. Thus, the divergent movement of the objects connected to the damper is converted from kinetic energy into thermal energy to rapidly dissipate the movement of the objects.
The foregoing example illustrates a damper that is very simple in design. However, dampers can be, and often are, much more complex. For instance, some dampers provide varying damping levels through the use of multiple chambers, peripheral passages, or electronic control systems.
Unfortunately, conventional dampers suffer from a number of limitations. First, these dampers are relatively complex and, as a result, are expensive, particularly if the damper is intended to be used only a single time.
Second, conventional dampers have a significant risk of failure when stored for extended periods of time without use. Seals between the chambers may deteriorate over many years of nonuse and fail when the damper is needed. In addition, these conventional dampers must be properly lubricated. Otherwise, friction between the piston head and chamber would inhibit or entirely prevent operation of the damper. Years of nonuse may also decrease lubrication and again result in product failure. Furthermore, a product failure in a vehicle safety system can be much more significant than failures in other areas. Thus, reliability of a damper used in a vehicle safety system is of the high importance.
Third, conventional dampers are not compact. In particular, the damping effect is generally proportional to the length or size of the damper. That is to say, longer and larger dampers generally provide a superior damping effect. As a result, dampers that provide a substantial damping effect are often bulky.
Consequently, it would be an advantage in the art to provide a damper that is simple in design and, thus, can be manufactured in a cost-effective manner. It would be an additional advantage to provide a motion damper that can be stored for long periods of time and still perform reliably when needed. It would be additionally advantageous to provide a damper that is compact, yet provides a significant damping effect.